When cutting a piece of material at a selected angle on a table saw, there is always a significant problem in achieving enough angular precision, e.g. to ensure a proper angle for tight joints. This problem has been addressed in a number of ways, for example as seen in the following U.S. patents: U.S. Pat. No. 4,454,793, issued June 1984, which relates to an attachment for a mitre gauge; U.S. Pat. No. 2,968,325, which relates to a table saw guide frame; U.S. Pat. No. 5,042,346, which relates to apparatus for fabricating accurate mitered corners; U.S. Pat. No. 4,165,668, which relates to a mitre gauge; and U.S. Pat. No. 5,275,074 which relates to a mitre slider.
In order to understand the nature of the problem, FIG. 1 is provided to show a typical plan view of a conventional table saw 11. Saw 11 typically has two parallel grooves 13 and 15 for restraining a miter guide 17 to be moved in a direction parallel to the groove. Miter guide 17 has a rotatably adjustable guide element 20 with a support surface 10 for setting the angle by which a piece to be cut is presented to the cutting element, in this case saw blade 23. Adjustable element 20 is pivoted on bar 18, which is configured to slide in groove 13. A hand-operated clamp nut assembly 19 also attaches to bar 18 at a different point than the pivot. By loosening clamp nut 19, rotating element 20, and tightening the nut, a user can adjust the miter to change the angle of the cut.
FIG. 2 shows a cross-sectional view of top 12 of table saw 11, and its relationship to mitre bar 18, and groove 13. As illustrated, in the typical table saw, the groove is rectangular in cross-section and the so is the mitre bar. In order to allow for ease of motion and to avoid the expense of creating bars and grooves with exacting tolerances, there is typically a significant gap between the bar and the groove, e.g. of the order of one-sixteenth of an inch. This "play", however, is a significant source of imprecision in consistently cutting desired angles with the saw, since the lateral motion of the bar in the guide changes the angle of the cut.
This lateral play problem is addressed specifically in U.S. Pat. No. 5,275,074 cited above. In that patent, however, the groove serves as a repository for a precision-shaped insert, and a mated bar is attached thereto. Although that apparatus does specifically address the problem, it is a very expensive, and requires adjustment by the operator to a achieve the appropriate sliding motion.
What is needed is a solution to the lateral play problem which is both inexpensive and requires a minimum of operator adjustment.